The overall objective of this project is to understand the growth factor requirements of SV3T3 cells in culture. Specifically, the work focuses on the purification and chemical and biological characterization of a low molecular weight (500-1000) serum growth factor (termed "Peak III"). Peak III has been partially purified by a method suitable for the treatment of bulk quantities of serum and by conventional gel filtration. New purification steps are being sought. The chemical nature of Peak III is presently obscure (no hexoses or amino acids). Further chemical analysis will include NMR and IR spectroscopy, gas chromatography coupled with mass spectrometry, elemental analysis, and other suitable microtechniques. Since Peak III does not affect the rates of DNA or RNA synthesis, it appears that it is more accurately described as a viability agent rather than as a growth factor. Other tests of its biological ability will include its effect on carbohydrate metabolism and nutrient uptake. The identification of another major serum growth factor ("Peak I") will be approached by comparison with a number of newly discovered growth active proteins. Finally, attempts will be made to replace serum completely through the use of media supplemented with these SV3T3 growth and viability factors.